The present invention relates to conveyor systems and, more particularly, to speed controlled infeed conveyor systems.
In conveyor systems employing a conveyor belt that delivers a column of edge-stacked articles (for example, cookies or crackers) onto an infeed apron or chute of a product handling machine, a certain axial pressure is necessary within the column to hold the articles in the vertical on-edge position. The axial pressure is a function of the relationship between the speed of the conveyor and the rate at which the articles are removed from the apron or chute by the product handling device. When the conveyor is trying to deliver articles to its output end at a rate that exceeds the actual removal rate, the product pressure increases. As the pressure builds, the column of articles will arch upwardly. If the pressure continues to build, the arch eventually will collapse. Many product pieces will be strewn on the floor and others will fall back onto the conveying surface in random orientation and will jam the system.
Where the edge-stacked articles are of uniform thickness and that thickness does not vary from batch to batch of the product, the product pressure can be held at a constant value simply by setting the conveyor speed to correspond to the speed of operation of the product handling device. However, in the manufacturing of crackers and cookies, the thickness does vary from batch to batch. Such variations are due to slight changes in the character of the ingredients, in the quantities used, or in the bake time or temperature. These changes are minute but when hundreds of crackers are stacked on edge, the cumulative effect becomes significant. The speed of the conveyor systems transporting the baked goods from the ovens to the packaging machines, is geared to that of the conveyor that carries the pieces through the oven. Whether the baked goods of a particular batch are thicker or thinner than normal, they flow out of the oven at the same rate. But a specific number of thick crackers produce a longer column than the same number of thin crackers, and thereby product pressure is effected.